Abstract
Heat shock factor-1 (HSF-1) activates transcription of heat shock proteins in eukaryotes. Several overlapping genomic clones containing the murine HSF-1 gene were isolated from a phage genomic library. Results indicate that the HSF-1 gene contains 13 exons that span at least 30 kilobase pairs. Sequence analysis of the 5'-untranslated region of HSF-1 suggests that it contains sequences of a recently described Bop1 gene in reverse orientation within its first 331 base pairs (bp) upstream of the translation initiation site. The minimal promoter sequence required for HSF-1 basal expression was identified by deletion analysis from -4 kilobase pairs to -331 bp of the promoter fused to a luciferase reporter gene using transient transfection assays. Results indicate that 331 bp upstream of the HSF-1 translation start site is required for maximal basal expression in NIH3T3 and F9 cells. This fragment also results in high levels of luciferase activity in the reverse orientation, that is, 5' to the Bop1 gene, suggesting that this segment is bidirectional and could be utilized for basal expression of both HSF-1 and Bop1 genes. This segment of the promoter contains recognition elements for Sp1 and CCAAT-box binding transcription factors, which when mutated in either sense or antisense orientations to the HSF-1 gene results in a reduction of basal expression by 50-75% relative to wild type, suggesting that these sites are critical for basal expression of both HSF-1 and Bop1 genes.
Highlights
The heat shock transcription factors (HSFs)1 have been cloned from a variety of organisms
Heat shock factor-1 (HSF-1) binds to conserved regulatory sequences known as heat shock elements, where it controls the expression of heat shock proteins in response to stress (9 –14)
The structure of the HSF-1 gene was deduced from a comparison of the known murine HSF-1 cDNA sequences and our genomic sequences
Summary
The heat shock transcription factors (HSFs) have been cloned from a variety of organisms. HSF in yeast is an essential gene, whereas in Drosophila it is not required for general cell growth and viability [1, 27], but it is required during oogenesis and early larval development [27] These data suggest that the function of HSF may not be solely to control transcription of heat shock proteins under stress conditions, but it may control the expression of non-heat shock genes under normal physiological growth conditions [27]. HSF-1 has been shown to activate transcription of various heat shock proteins in response to heat shock as well as other environmental stresses [5, 7, 14]. These are alternate splice variants of HSF-1 and HSF-2 that recently were shown to be expressed differentially during development [35]
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call